Interactive television (TV) systems are known from for example U.S. Pat. No. 5,233,654. The system described in the '654 patent includes a receiver having a computer with sufficient storage to store interactive programs, albeit that provision is made to alter the programs with transmitted data. In order to make interactive TV less costly and therefore more attractive to consumer acceptance, it is desirable to keep memory in the receiver to a minimum. This may be achieved by regularly transmitting executable code for the desired applications, rather than requiring that the applications be continuously stored in the receiver. In effect the transmission media is utilized as a mass storage device.